Analog Devices Inc. LT3965EFE#TRPBF

Overview

LT3965EFE#TRPBF from Analog Devices is an 8-channel LED bypass switching IC for precision dimming of individual LEDs in high-voltage strings using a common current source. It integrates eight floating-source 17V/330mΩ NMOS switches, supports I²C multidrop (16-device bus), delivers 256:1 digital PWM dimming with optional 11-bit logarithmic fade, and reports open/shorted LED faults per channel. It is used in automotive LED headlight clusters requiring flicker-free, fault-resilient dimming control.

For engineers reviewing the LT3965EFE#TRPBF datasheet, LT3965EFE#TRPBF pinout, LT3965EFE#TRPBF application, or LT3965EFE#TRPBF equivalent, key selection criteria include VIN range (8–60V), VDD logic supply (2.7–5.5V), per-channel fault thresholds (programmable 4.5–18V open LED, 1–13.7V shorted LED), fade-enabled PWM resolution, and AEC-Q100 qualification for automotive thermal and reliability compliance.

Technical Context

The LT3965EFE#TRPBF implements independent per-channel control logic with dual-mode PWM: standard 8-bit dimming (256 steps) and logarithmic 11-bit fade transition (up to 100 steps), synchronized to an internal oscillator (RTCLK resistor-programmed) or external clock source divided by 2048. Each channel's NMOS switch operates with 330mΩ R_DS(on) and supports DRN–SRC voltage up to 25V, enabling safe bypass of up to 17V across one or more series LEDs.

Fault detection is fully programmable: open LED threshold (VOTH[1:0]) selects 4.5V/9V/13.5V/18V; shorted LED threshold (VSTH[1:0]) scales with LEDREF input (0–4V), yielding four fixed offsets (1V, VLEDREF+1V, 2×VLEDREF+1V, 3×VLEDREF+1V). Faults trigger ALERT assertion and automatic channel override-open LED forces switch-on to maintain string continuity; shorted LED preserves dimming while flagging error.

Key Specifications

Pinout & Package

LT3965EFE#TRPBF is housed in a 28-lead plastic TSSOP package with exposed pad (Pin 29 = GND), θ_JC = 10°C/W. The exposed pad must be soldered to PCB ground plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LED bypass switching applications.

Compared with LT3965IFE#TRPBF, the LT3965EFE#TRPBF adds AEC-Q100 certification and automotive reliability reporting; compared with MAX16832ATL+, it delivers 8× finer dimming resolution, perceptually optimized fade, and native I²C multidrop support-critical for scalable, high-fidelity LED lighting systems.

Availability

LT3965EFE#TRPBF is available at Aetrix Electronics and suitable for automotive LED headlight clusters, large-format LED displays, automated camera flash equipment, and RGBW color-mixing lighting requiring stable component supply, long-term lifecycle assurance, and AEC-Q100-compliant sourcing.

Supply support for LT3965EFE#TRPBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement, power management, and connectivity.

The LT3965EFE#TRPBF belongs to Analog Devices' Power by Linear™ LED driver and control product line, engineered specifically for fault-tolerant, high-reliability automotive and industrial LED lighting systems demanding programmable per-channel dimming and robust diagnostics.

FAQ

What is the default power-on state of the LT3965EFE#TRPBF?

The LT3965EFE#TRPBF initializes all eight NMOS switches in the OFF state (LEDs illuminated) upon power-on reset. This behavior corresponds to the LT3965 variant-not the LT3965-1, which defaults to all switches ON. The default open LED threshold is 18V (VOTH[1:0] = "11"), and the I²C address defaults to 0x2F (ADDR[4:1] = 1111). All registers load factory-default values defined in Table 1 of the datasheet.

How does the LT3965EFE#TRPBF handle an open LED fault?

When the LT3965EFE#TRPBF detects an open LED condition-defined as DRN–SRC voltage exceeding the programmed VOTH threshold-it asserts the ALERT pin low and automatically turns ON the associated NMOS switch to bypass the faulty LED. This maintains current flow through the string and prevents overvoltage on remaining LEDs. The fault remains latched until cleared via I²C write to the fault status register.

Can the LT3965EFE#TRPBF drive LEDs directly, or does it require an external current source?

The LT3965EFE#TRPBF does not source LED current; it functions exclusively as a bypass switch. It must be used with an external constant-current LED driver (e.g., LT3955 buck LED controller) that supplies regulated current to the LED string. The LT3965EFE#TRPBF shunts current around selected LEDs via its NMOS switches, enabling per-LED dimming without altering the main string current.

What is the maximum number of LT3965EFE#TRPBF devices supported on a single I²C bus?

Up to 16 LT3965EFE#TRPBF devices can share one I²C bus using the four ADDR[4:1] pins to configure unique 7-bit slave addresses. Each pin defaults high (1111), yielding base address 0x2F; grounding any combination produces distinct addresses in the 0x20–0x2F and 0x50–0x5F ranges. No external level shifters or bus buffers are required for this configuration.

Does the LT3965EFE#TRPBF support both internal and external PWM clock sources?

Yes, the LT3965EFE#TRPBF supports dual-clock operation via the RTCLK pin. Connecting a resistor (e.g., 28kΩ) to GND enables the internal oscillator, setting PWM frequency (e.g., 500Hz). Driving RTCLK with an external square wave (2.5MHz max, 0.4V low / 1.5V high thresholds) overrides the oscillator, and dimming frequency equals the external clock divided by 2048. The pin must never be left floating.